THERE ARE AS MANY RECIPES FOR COOKED TOMATO SAUCES in Mexico as there are for meatloaf in the United States! In Yucatán, the choices are somewhat more narrow. The basic differences between the two most popular ones are that in the first (Salsa de Jitomate Yucateca I) the vegetables are charred and the onions caramelized, giving the sauce a wonderfully smoky taste; and in this version, the uncooked vegetables are all pureéd together, then poured into hot oil for the final cooking and thickening. The result is creamy, rich and versatile enough to be served with any dish calling for a cooked tomato sauce.